The invention relates to an interlinking system for overhead transfer devices having at least two portals for the transport of workpieces or of workpieces on pallets between machines and/or supply/removal devices and vice versa. Each of the portals is in this respect equipped with a loading unit and the two portals are equipped with a transfer module for conveying the workpieces or the workpieces on pallets between a first and a second portal which is in turn equipped with a transport device for taking up one or more workpieces or workpiece pallets.
In the mass production of workpieces, in particular in the mechanical machining of workpieces, they are as a rule supplied in accordance with an exactly planned production flow to machine tools for carrying out a specific production operation sequence. For this purpose, the workpieces are first channeled at a supply device into a production system and are then transported onward in a fully automated manner within this system from one machining flow to the next. Depending on the number of production operations, the workpieces are either handed over from the production system via a handing-over apparatus or are transferred via an intermediate automated process to a following production system for carrying out further machining operations at the end of the machining.
Depending on the product group with which the workpieces can be associated, certain production systems with interlinking devices such as belts, portals, palleting cells having floor rollers or similar automated devices have proven themselves in the industry. For the machining of crankshafts, engine blocks or cylinder heads, portals for linking machine tools are frequently used, with these portals usually running above the machines for the loading of the machine tools.
The individual machine tools are supplied with workpieces using these portals, with frequently a plurality of redundant machine tools being set up next to one another beneath a portal for reasons of a flexible production volume adaptation for the parallel machining of the same production flows. It is thus possible to respond flexibly to different production quantities in that individual machines are simply switched off and on with low production volumes and in that the loading unit at the portal travels over these machines without carrying out a loading. Equally, machines which were switched off for maintenance or service purposes can easily be taken out of production without the total production line therefore having to be switched off. A flexible production quantity adaptation can take place by the possibility to travel to or to travel over the transfer positions at the machines individually using production systems of this type of construction.
A number of advantages can also be seen here on the process changeover of the production system. Redundant machines can thus already be taken out of production in part and be changed over, while the current series is still finally machined on the parallel machine.
The arrangement of the machines is first selected in accordance with the machining order. Furthermore the machine set-up must, however, also be orientated on the local circumstances and construction conditions. Support columns for higher floors or for a hall ceiling, hall length or available installation areas for the production system thus influence the extent of the automation or partly limit their lengths. Due to the installation and the construction type of the machines, the extent of the upwardly disposed automation is consequently then defined even more exactly since the transfer/takeover position of the machine likewise determine the portal development.
Furthermore, even further demands are made on the automation which results from demands such as the transfer precision of the loading unit to the workpiece mount of a machine tool, permitted temperature expansion or length position of the portal carrier, length of a cable drag chain for the electrical supply of the loading unit and simpler marginal conditions. Since a plurality of charging units frequently travel simultaneously on the portal, this also has an influence on the portal length via the maximum permitted vibrations and the permitted travel speeds resulting from this or the demands on the positioning precision. All these marginal conditions additionally limit the portal length in addition to the local demands.
In practice, the portals are therefore split into sections between which the workpieces are conveyed from one portal to the next by a further automation, frequently a floor automation. This automation can comprise a plurality of possible transport devices such as bands, shuttles, accumulating roller conveyors or similar devices.
In DE 10 2007 009 329 A1, a machining line is shown having a plurality of machining machines which are connected to one another via a transport path on which a plurality of charging units can be traveled. The charging units convey the workpieces from a charging point to the individual machines in order then to place the finished workpieces down at an unloading station after the machining. This classical design of a portal device is selected with many interlinking systems having an overhead transfer device for the transport of workpieces. In this case, however, only one single portal is shown having a receptions station and an unloading station for the interlinking of machine tools.
EP 1 125 684 A1 shows a production system having a plurality of portals which are directly connected by means of stacked cells. In this arrangement, the individual workpieces always first have to be placed down in parts carriers within the stacked cell. The filled parts carriers are then restacked by a transfer device from one stacked position to the stacked position disposed next to it before they can be taken up there by the other portal. This system is above all suitable for small, light workpieces having short machining cycle times and is frequently realized in the mass production of automobile transmissions and here frequently in gear production for transmissions.
With large, heavy workpieces, the storing of individual workpieces in mesh baskets is not suitable for stacked cells. Equally, due to the frequently longer machining times for the individual parts, much fewer workpieces are within a production cell in the production so that a direct transfer of individual workpieces is required between the portals. The intermediate storing of the workpieces is here of secondary importance in its weighting to the direct parts transfer of the workpieces as an evaluation criterion in the selection of the automation.